The present invention relates generally to a portable apparatus for blowing and vacuuming outdoor areas.
Portable leaf blowers are used to sweep outdoor areas of leaves, grass clippings, and other debris using high velocity air. They include a motor, such as an electric motor or an internal combustion engine, and a fan driven by the motor that generates airflow from an inlet of the housing to an outlet of a housing. The fan is typically a centrifugal impeller in a housing in the shape of a volute. Air flows into an opening formed in a side wall of the housing, generally in the direction of the axis of the impeller, and then outwardly into the housing in directions that are generally perpendicular to the axis of the impeller. The air is then collected and directed toward an exit opening by an outside wall of the housing.
Some portable leaf blowers are designed to operate in either of two modes, blower or vacuum. These devices are sometimes referred to as xe2x80x9cconvertible blower/vacuumsxe2x80x9d or xe2x80x9cblower/vacs.xe2x80x9d In a blower mode of operation, an elongated tube is attached to the housing outlet. The tube has an exit opening near the ground in order to deliver a concentrated column of high velocity air near the ground. In a vacuum mode of operation, an elongated tube is secured to the housing inlet and a debris collection bag is attached to the housing outlet. The term xe2x80x9cleaf blowerxe2x80x9d will be used to refer to both single mode blowers and dual mode convertible blower/vacuum units.
When sweeping leaves, it is desirable to be able to change the velocity of the air coming out of a leaf blower. Internal combustion engines inherently permit control over the air velocity by means of their throttles. Leaf blowers powered by electric motors, however, typically have a two position xe2x80x9con/offxe2x80x9d switch or a switch that also provides two, discrete speed settings, xe2x80x9chighxe2x80x9d and xe2x80x9clow.xe2x80x9d Some electrically powered leaf blowers mechanically restrict the size or area of an inlet or an outlet opening to reduce air flow rates.
Mechanical air flow rate control devices on electric leaf blowers that restrict air flow have several shortcomings. They are, for example, relatively cumbersome to operate and typically require one hand to hold the device and a second hand to manipulate the mechanical air restrictor. Some devices only have two positions, open and closed, which do not provide sufficient control for some users.
The present invention is directed generally to an electric leaf blower having an improved air speed control overcoming one or more of these and/or other shortcomings. According to the invention, an electric leaf blower includes an operator-controllable circuit for continuously varying the speed of an electric motor rotating a fan of over at least a range of speeds, thereby allowing the user to control the speed of the air flow at the outlet of the leaf blower.
In a representative example of a leaf blower employing a preferred embodiment of the invention, a thumb wheel or other element suitable for generating a signal to a power control circuit for an electric motor is mounted for access by a user while the blower is being operated. Preferably, it is mounted in a handle of the leaf blower in order to allow a user to continuously vary the speed of the electric motor without requiring the user to stop blowing leaves or to use the other hand to make the adjustment. A power control circuit regulates the power supplied to, and thus also the speed of, an electric motor connected to a fan of a leaf blower. To dissipate heat generated by one or more components of the control circuit, the one or more heat generating components are preferably mounted on a heat sink that is mounted to an inside wall of a housing of the blower""s fan, to be cooled by air currents generated by the fan.
These and other aspects of a preferred embodiment of the invention and their respective advantages are described below in reference to a representative leaf blower.